Selective switch



June 21, 1,540,059 1 R. D. CONWAY SELECTIVE SWITCH Original Filed Dec.5, 1921 3 Sheets-Sheet l June 1925. 1,540,059 R. 0. CONWAY SELECTIVESWITCH Original Filed Dec. 5, 1921 3 Sheets-Sheet 2 Patented June 2,1925.

I UNITED STATES PATENT oFFicE.

MY ID. CONWAY, OF BERNARDSVILLE, NEW JEMEY, "ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW- YORK, N. Y., A CORPORATION OFSELECTIVE SWITCH.

Original application filed nu bers,

To all whom it may concern."

Be it known that I, ROY D. CONWAY, a citizen of the United States,residing at Bernardsville, in the county of. Somerset, State of NewJersey, have invented certain new and useful Improvements in SelectiveSwitches, of'which the following is a full, clear, concise, and exactdescription. This invention relates to selective switches andparticularlv, to cross-bar switches used for the selection andconnection of'balancing networks in repeating circuits, and is adivision of application Serial No 519,864, filed December 5, 1921, byRoy D. Conway.

The object of the invention] is to provide an efficient, simple and.rugged switching means which will establish connections in both, itsnormal and operated positions.

A. feature of the invention is the use of back contacts for the flexiblecontact fingers of a cross bar switch whereby such fin- J. N. Reynolds1,238,194, August 28, 191.7,.

entitled Automatic switch? This, switch comprises vertical bars such as1 shown in Fig. 4 and shown diagrammatically 1n Flg, 3, and compriseshorizontal bars such as 2 shownin Fig, 4 and shown diagrammatically Forreasons which willbe made in Fig. 3. apparent hereinafter, 'thevertical'bars may with propriety be hereinafter termed cord bars andthehorizontal bars may appropriately be hereinafter termed I net bars. Eachofthese vertical bars comprises a plurality of Vertical metallic stripconducting members havingprojeeting spring contacts such as thosedesignated 3 in Fig. 4, and

each of the horizontal bars compriseshorizontal metallic stripconducting members having contact projectionssuch as those designated4in 4. The vertical bars are 1921, Ser al N 5,1 ,864.. Divided and thisapplication filed October 15, 1923., Serial No. 668,732.

mounted'in the frame (not shown) of the.

cross-bar switch by means of vertical pivots such as Each horizontal bar2 is supported from theframe (not shown) of the cross-bar switch bymeans of" members 6, rigidly attached to the frame, .and link 7. Thelink 7 is pivoted to members 6 by pin 8 and to bar 2 by pin 9. Thespring 10 normally presses the bar 2' lengthwise toward the right asviewed in Fig. 4, but the bar 2 may be moved lengthwise toward the leftas viewed in Fig. 4 by armature 11 of electromagnet 12 when theelectromagnet is energized. This armature is in the form of a bell cranklever pivoted at 13 in the frame of the cross-bar switch and bearingagainst the pin 9. A spring 14 normally biases the bar 1 in a counterclockwise direction as viewed from above in Fig. 4. Upon the energization of the electromagnet 15, the armature 16 thereof overcomesthe biasing action of spring 14. The armature 16 is mounted in the frameof the cross-bar switch by a pivot 17.

In the operation of the switch, magnet 15 turns bar 1 clockwise toposition spring contacts 3' for subsequent engagement of their ends bycontact projections 4, and magnet 12 moves bar '2 lengthwise to engagecontact projections4 with that set of contacts 3 located at theintersection of bars 1 and 2. Upon the deenergization of magnet 15,spring 14 turns bar 1 counterclockwise looking down upon Fig. 4, torestore bar 1 to a positionin which the ends of all of its sets ofcontacts 3 except the engaged set are out of the line of movement ofcontacts such as 4. p

Bar 1 carries a strip 18 of insulating material in which are mountedconducting plates 19 for bridging across contacts 3. lVhen contacts 4engage spring contacts 3, the latter are moved out of engagement withplates 19. The purpose of providing bridging plates 19., and the mannerin which magnets 1'5 and 12 are energized will be made apparenthereinafter.

' The magnets, such. as 15, which actuate the vertical or cord bars maybe termed cord bar magnets, and the magets, such as 12, which controlthe horizontal or net bars may be termed net bar magnets. It will beexplained below that each of the net bar magnets comprises twomagnets, anet bar pick-up magnet and a net bar locking magnet.

In the diagrammatic showing of the crossbar switch in Fig. 3, the netbars are designated 2, 2, 2 2 2 etc., reading from the top of the figureto the bottom of the figure, and the cord bars are designated 1, 1, 1',1, reading from right to left. In Fig. 3, the spring contacts of cordbar 1, generally considered, are designated 3, those of cord bar 1generally considered, being designated 3 those of cord bar 1", enerallyconsidered, being designated 3*, etc. Certain ones of these springcontacts are, for convenience, designated by various referencecharacters individual to the spring contacts to which they are applied.The contact projections of net bar 2, generally considered, aredesignated 4, those of net bar 2 generally considered, being designated4", those of net bar 2, generally considered, being designated 4, etc.Certain ones of these contact projections are. for convenience,designated by various reference characters individual to the contact.projection to which they are applied.

Referring to Fig. 1, repeaters such as R and R, which may be of anysuitable type such as the wellknown vacuum tube repeaters, are employedto interconnect lines such as L L L, and L,. Referring to Fig. 3,networks for balancing these lines are shown at 21, 22, 23, 24, 25, 26and 27. Networks 21, 22 and 23 may be building out sections or may bebalancing sets for composite or phantom apparatus. Networks 24 and 25may be building out sections or may be basic networks. Networks 26 and27 may be for instance, basic networks having impedances different fromthose of networks 24 and 25. As appears from Fig. 3, each of the netbars of the cross-bar switch has connected thereto one of the networks21 to 27. It will be understood, of course, that the drawing does notshow all the cord bars or net bars and networks which may be included ina single cross-bar switch.

The operation of the system in selecting suitable balancing networks andconnecting them to the lines L, and L, will now be described, on thesupposition that the operator inserts plugs P and P into the jacks oflines L and L, to connect these lines through repeater R. Upon theinsertion of plug P in the jack of line L,,, magnet 30 is energized bycurrent flowing in the circuit from ground through battery 31,resistance 32, magnet 30, lead 33, sleeve conductors of plug P and thecooperating jack, lead 34 and winding of magnet 35 back to ground.Magnet 30 attracts its armature, but the closing of this contact doesnot complete any circuit. Magnet 35 does not attract its armatures atthis time, because the resistance 32 reduces the current flow frombattery 31. Upon the in sertion of plug P into the jack of line L,,magnet 36 is energized over the following circuit: from ground throughbattery 37, resistance 38, winding of magnet 36, lead 39, sleeveconductors of plug P and the cooperating jack, lead 40, winding ofmagnet 41 back to ground. Magnet 41 does not attract its armatures atthis time, because the resistance 38 reduces the current flow frombattery 37. The magnet 36 attracts its armature closing a circuit formagnet 42 as follows: from ground through battery 43, armature 44 ofmagnet 45, lead 46, lead 47, contact spring 48 of magnet 49, lead 50,armature 51 of magnet 36, lead 52, armature of magnet 30, lead 54,contact spring 55 of magnet 56, lead 57, winding of magnet 42, lead 58,lead 59, armature of magnet 61 and lead 62 to ground. Each of themagnets 45, 42 and 61 is individual to a repeater cord circuit, magnets45 and 61 being operated in the same fashion as magnet 42. Only one ofthese magnets can be in the operated condition at any given time, aswill be readily apparent from the arrangement of the armatures of thesemagnets in the battery lead 46 and ground leads 59 and 62 as shown inthe drawing. There will of course be one magnet such as the magnet 45,42 and 61 for each repeater cord circuit. It will be made apparenthereinafter that since only one of the magnets can be in the operatedcondition at any given time the operation of selecting balancingnetworks and connecting them to a repeater can take place for only onerepeater at a time. Thus, magnets such as 45, 42 and 61 insure that thenetwork selecting and connecting operation for one repeater will befinished before such operation can begin for another repeater.

\Vhen magnet 42 has been energized as mentioned above, it att acts itsarmatures 63, 64 and 65 causing line selection control relay 41 toattract its armatures 94, 104 and 113. This operation of magnet 41 isdue to the energization of this magnet over the following circuit: fromground through battery 43, armature 44, lead 46, armature 64, lead 66,lead 67, armature 68 of retarded relay 69, lead 70, armature 63, lead71, winding of magnet 36, lead 39, sleeve conductors of plug P and thecooperating jack, lead 40 and winding of magnet 41 to ground.

The attraction of armature 64 of relay 42 as mentioned above also causesthe cord bar magnet 15", which is like the cord bar magnet 15, shown inFigs. 3 and 4, to attract its armatures 16, 72 and 73, the circuit forenergizing this cord bar magnet 15 being as follows: from ground throughbattery 43, armature 44, lead 46, armature 64, lead 66, lead 67, lead74, lead 75, armature 76 of retarded relay 49,1ead 77, lead 78, contactsprings 283, 284 and 285 cross bar winding of magnet 15".to ground. Theattraction oi the armature 16 by cord bar magnet 15*, causes the cordbar 1 to turn on its pivots to positionits spring contacts 3 forsubsequent engagei'nent of their ends by contacts ofa net bar in thefashion described above in connection with Fig. 4;. i The attraction ofarn'n ture 73 by magnet 15", and the attraction of armature 94 of lineselection control relay 41, both as men tioned above, causes theoperation of mag nets 79 and over the following circuit: from groundthrough battery 43, armature 44, lead 46, armature 64, lead 66, leads67, 74 and 75, armature 76, leads 77 and 81, winding of magnet 79, lead82, armature 73, lead 83, lead 84, lead 85,.armature 86, contact spring87, winding ofnet bar pick-up magnet80, lead 88, contact spring 89,armature 90, lead 91, lead 92, lead 93., and armatures 94 of line,selection control relay 41 to ground. The net bar pickup magnet winding80 forms part of the net bar magnet 12, shown in Fig. 4 and also in Fig.3, each net barmagnet' comprising in addition to a pick-up magnetwinding, a locking magnet winding such as is shown at 114 in Fig. 3.Upon the energizati-on oi the pickup magnet winding 80 of magnet 12, asjust mentioned, the netbar 2 is moved longitudinally toward thjeleft to.engage contact projections 159, 119, etc., with contact springs 158,118, etc., (these projections and springs being located at theintersection of bars 2 and 1*), all in the general fashion describedabove in connection with Fig. 4.

- The attraction of armature 73 by cord bar mag-net 15 and: theattraction ofv armature 104by line select-ion control relay 41, both asmentioned above, causes the operation of net bar pick-up magnet 95, theenergizing circuit for this magnet being from battery 43 to lead 84 asjust traced and thence through lead 96, armature 97, contact spring 98,winding of magnet95, contact spring 199, armature 100, lead 101, lead102,.lea'd103, armature 1 04 toground. Thereupon the net bar 2 is movedto engage contact projections 17 3, 125, etc.. with contact springs 172, 124, etc.

The attraction of. armature 7310f] magnet 15 andtheattraotion ofarmature113 of line selection control relay 41, both as mentioned above, causethe operation'of'net bar pick-up magnet 105, the energizing circuit forthis magnet being from battery 48 to.

lead 84 as traced above and thence through lead 106, armature 107,contact spring 108,

upon the net; bar 2? is. inoved'to engage contact projections 186, 131,etc, with contact springs 185, 130, etc.

The energization oil not bar pickup magnet winding 80, as mentionedabove, causes the attraction of its armatures 86, and 161. The armatures86 and 90 each break the original energizing circuit, or piclz upcircuit, which passed through windings off iagnets 79 and 80. However,before such circuit is broken, armature 86 allows contact spring 87 tocontact with a terminal of the coil of magnet 114, and armature 90allows contact spring 89 to contact with lead 122, and moreover, contact119 has engaged contact 118, as mentioned above; and, therefore, alocking circuit, including the wind.- ing of pick-up magnet 80 and thewinding of locking magnet 114 in series, is closed for net bar magnet12, this locking circuit being as follows: from ground tl'irouglibattery. 48, armature 44, lead 46, arn'iature 64, leads 66, 67 and 74,armature of magnet 79, leads 115 and 116, cord bar conducting member.117, cord bar contact 118, net bar contact 119, net bar conductingmember 126, lead121, winding of net bar locking magnet 114, armature 87,winding of net bar pick-up magnet 80, lead 88, armature 89, lead 122 toground. As soon as armature 86 has. become disengaged from contactspring 87 (and armatures 97 and 107 have similarly and sii'nultaneouslydisengaged contacts 98 and 108, due to the energization, as mentionedabove, of magnets and 1.05), magnet 7 9 is deenergized and therefore thecircuit justtraced from lead 74 to lead 116 is broken at the armature ofma net 7 9' but b 7 a locking circuit for not bar magnet 12 ismaintained, for a circuit from lead 74 to lead 116 is maintainedthrough. the follow ing path between lead 74 and lead 116: from lead 74through lead 75 and resistance 135 to lead 116. Moreover, a new circuitbetween lead 74 and lead 116 is established through the back contact ofthe armature of magnet 7 9 and the winding of magnet 69.

The energization of net bar pick-up magnet 95, as mentioned above,-results in the establishing of a locking circuit for magnets 95 and 123just as, in the manner described above, the energization of netbarpiclcup magnet 80 resultsin the establishing of. a locking circuitfor magnetsSO and 114. The locking circuit t or magnets 95 and 123 is asfollows: from battery 43 to cord bar conducting member 117, as in thecaseof the locking circuit for magnets 80 and 114, thence through cordbar contact spring 124, net bar contact projection 125, net barconducting member 126, lead 127, winding of magnet 123, contact spring98, winding of magnet 95, contact spring 99, lead 128, to ground.

Theienergization of net bar pick-up magnet 105, as mentioned above,results in the establishing of a locking circuit for magnets 105 and 129just as, in the manner described above, the energization of net barpick-up magnet 80 results in the establishing of a locking circuit formagnets 80 and 114. Th locking circuit for magnets 105 and 129 is asfollows: from battery 43 to cord bar conducting member 117, as in thecase of the locking circuit for magnets 80 and 114, thence through cordbar contact spring 130, netbar contact projection 131, net barconducting member 132, lead 133, winding of magnet 129, contact spring108, winding of magnet 105, contact spring 109, lead 134 to ground.

As has been mentioned above, the energization of net bar pick-up magnets80, 95 and 105, causes the deenergization of magnet 7 9 by openingbranches of the circuit for magnet 79 at armature 86 and contact 87,armature 97 and contact 98, and armature 107 and contact 108, and thearmature of magnet '79 then closes a circuit through the coil of magnet69. Slow operating magnet 69 then attracts its armature 68 thus breakingthe circuit traced above through battery 43 to marginal relay 41 andcausing relay 41 to release its armatures, resistance 38 preventing thecurrent fr'om battery 37 through winding of relay 41 from beingsuflicient to maintain relay 41 operated. If magnet 69 were not slowoperating, then upon the enen gizat'ion of winding 80 and the consequentclosing of contacts 118 and 119 and engagement of contact spring 87 withone terminal of magnet 114 (all as described above) mag net 69 mightpossibly receive current through the armature of magnet 79 before thelatter armature left its back contact, and therefore the armature ofmagnet 69 might possibly be picked up before magnet 79 had picked up andreleased.

The attraction of armature 68 as mentioned above also closes theenergizing circuit for slow operating relay 49 as follows: from groundthrough battery 43, armature 44, lead 46, armature 64, lead 66, lead 67,armature 68 and winding of magnet 49 to ground.

The energization of relay 49 attracts its armature 76 thereby openingthe circuit traced above from battery 43 to lead 77. This opens thecircuit traced above through winding of cord bar magnet 15, whereupon aspring (not shown) corresponding to spring 14 of Fig. 4, returns thecord bar 1" to its normal position, but the sets of spring contacts 3which have been engaged by contacts 4, 4 and 4 of the net bars 2, 2 and2 remain in such engagement.

Th energization of magnet 49 as mentioned above opens the circuit tracedabove from battery 43 through winding of magnet 42 at contact spring 48,but closes a circuit for magnet 42 from battery 136 through armature137, contact spring 48, lead 50, armature 51, lead 52, armature 53, lead54, contact spring 55, lead 57, winding of magnet 42, lead 58, lead 59,armature 60, lead 62 to ground.

The attraction of armature '76 of relay 49 as mentioned above alsocauses the operation of marginal line selection control relay 35, theoperating circuit for relay 35 being as follows: from ground throughbattery 43, armature 44, lead 46, armature 64, lead 66, lead 67, lead74, lead 75, armature 76, lead 137, armature 138 of retarded relay 139,lead 140, winding of magnet 30, lead 33, sleeve conductors of plug P andthe cooperating jack, lead 34, lead 35 to ground. The purpose in havingmagnet 49 slow operating is to delay the closing of the contacts of lineselection control relay 35 until after the contacts of line selectioncontrol relay 41 are open.

The operation of relay 49 as mentioned above and the consequentattraction of its armatures 7 6 and 142 also causes the operation ofcord bar magnet 15 over the following circuit: from ground throughbattery 43, armature 44, lead 46, armature 64, leads 66, 67, 74, 75,armature 76, armature 142, lead 144, armature 145 of relay 56, lead 146,lead 147, winding of magnet 15 to ground. Magnet 15 thereupon operatesits cord bar 1 and also its armatures 148 and 149.

The function of armature 148 will be made apparent hereinafter.

The attraction of armature 149 and the closing of the contacts of lineselection control relay 35 cause the energization of magnet 150 and netbar pick-up magnet 151 over the following circuit: from ground throughbattery 43, armature 44, lead 46, armature 64, leads 66, 67, 74, 7 5,armatures 76 and 142, lead 144, armature 145, lead 146, lead 152,winding of magnet 150, lead 153, armature 149, lead 154, lead 84, lead155, armature 141, lead 156, conducting member 157 of cord bar 15,spring contact 158, contact projection 159, lead 160, armature 161, lead162, armature 163, contact spring 164, Wind ing of pick-up magnet 151 ofnet bar 2, lead 165, contact spring 166, armatures 167 and 90, lead 91,lead 168, lead 169, and armature 170 of line selection control relay 35to ground.

The attraction of armature 149 by cord bar magnet 15 and the closing ofthe contacts of line selection control relay 35 as mentioned above alsocause the energization of net bar pick-up magnet 171 over the followingcircuit: from battery 43 to conducting member 157 of the cord bar 1, asjust traced, thence through spring contact 172, contact 173, conductingmember 174,

' lead 1.7 5, armatnre's 176 and 177, contact spring 178, winding of netbar pickup magnet 171, cont-act spring 179, armatures 180 and 100, leads101, 181, and 182,'armature 1'83 toground. I I v The attraction ofarmature 149 by cord bar magnet 15 and the closing of the con tacts ofline selection control relay 35, as mentioned above, also 'cause; theenergiza tion ofnet bar pick-up magnet 1840ver the following circuit:from battery 43 to cord bar conducting member 157, as traced above, andthence through spring contact 95, contact projection 186, netbarconducting member 187, lead 188, a'r 'nat'ures 189 and 190, contactsprin 191, Winding of net bar pick up niagnetl 4, contact sprin'g 192,arma; tnres 193 a11d 110,1'e'ads 111, 194 and195', armature 196' toground. 1 v Upon the fenergizatioir of net bar pickup magnet 151', asmentioned above, net bar 2 is moved to the left; as viewed in 3 toengage a set of it's contact projections with a set of springcontacts'on the cord bar 1, which is now being held in operated positionby corn bar magnet Similarl upon the energization of magnets 171 and184, as mentioned above,*the net bars 2 and 2 corresponding to thesemagnets respectively are moved to the left as viewed in Fig.3 and a setof contact projections on each of these bars engagesja set ofspringcontacts on'the cord bar 1. a

The energization of magnet 150-, and the energization of pick-up magnet151 andthe 'consequentoperation of net bar 2?,all as mentioned above,cause the 'energiiation of net bar locking magnet 197 over'the'following circuit: from battery 44, lead 46, armature 64, lead 66,lead 67 ,lead 74, lead 75, armature 76, armature 142, lead'14'4, lead198 armature of magnet 150, lead 199, lead 200, cord barconductingmember 201, spring contact 202, contact 203,net bar conductingmember 204, lead 205,"Winding of magnet 197, armature 164, winding of manet 151, armature 166' and 205 to ground. imilarly the energizatioi'i ofmagnet 150', and the energi zation of pick-up magnet 171 and theconsequent operation of net bar 2, all as mentioned above, cause theenergi'zation of netbar locking magnet 206 overthe following circuitfrom battery 43'to cord bar con-v ducting member 201-, asjust traced,and thence through spring contact 207, contact 208,net bar conductingmember 209, lead 210, winding of magnet 206, armature 178, winding ofmagnet 171, armature 17 9, and

1 lead 211 to ground; Similarly the energize tion of magnet 150 and theenergization of pick-up magnet 184 and the consequent operation of netbar 2','fall as mentioned above,

' cause the energi'zation-off net bar locking 1mignet212 overthejfollowing circuit from battery 43" to cord bar conductlng member201, as traced above, and thence through spring contact 213, netbar-contact 214, net bar conducting member 215', lead 216, Wind ing ofmagnet 212, armature 191, winding of magnet 184, arn' ature192, and lead217 to ground. That part of the circuits traced above for lockingmagnets197, 206 and 212 which comprises, lead 198, armature of magnet150 and lead 199 is shunted by a resistance 218.

The operation of the pick-up magnet 151, as mentioned above, attractsthe armature 163 of the magnet, thereby breaking the initial operatingcircuit of the magnet at armature 163. Similarly, theoperation ofmagnets 171 and 184 break the initial operating circuits of thesemagnets at armature 177 and 190, respectively. The breaking of all ofthese branches of the circuit through magnet 150 causes that magnet torelease its armature thereby opening the contactbetween the armature andlead 199 and connecting winding of retarded relay 139- (instead of lead199) in parallel with resist; ance 218 in a circuit supplying current tothe locking magnets 197, 206 and 212. Magnet 139' thereupon attracts itsarmature 138 andthus causes the breaking of the circuit traced abovefrom battery 43 through Winding of marginal line selection control relayand thereby causes line selection control relay 35 to' release itsarmatures. The purpose in making magnet 139 slow operating is to' insurethat this magnet will not be operated before magnet 150 has picked up iand released.

The operation of relay 139, as mentioned above, also closes thefollowing energizing circuit for relay 56: from ground through battery43, armature 44', lead 46, armature 64, leads 66, 67, '74, 75, armature'76, lead 137, armature 138, leads 219 and Winding of niaigi'iet 56 toground.

Relay 56 then attracts its armature 156 thereby opening the circuittraced above for cord bar magnet 15 The cord bar ,1 re;- turns to itsnormal position. However, the sets of spring contacts this cord barwhich are in engagement with net bar contacts at the time magnet 15 isdeenergized, remain such engagement. t v The-energization of rel-(13 56,as mentioned aboye, attracts armature 220 of the relay Cir therebybreaking the circuit of Winding of magnet 42 at contact 55, thuscausing,the bi' eaking at 64 of the connection traced above from battery43 to lead 67. However, before thisbreakat 64 occurs, armature 220 byengaging spring contact 55 connects battery 136 (I magnets 139 a d; 56,and the pic-leap locking magnets of net bars 2 2 and 2 are maintainedenergized from battery 136 until the circuit traced above from battery136 to lead 67 is broken at armature 51 or 53 by the deenergization ofmagnet 36 or 30, due to the removal of plug P or P.

The breaking of the circuit of magnet 42, as mentioned above, releasesits armatures 64 and 65, whereupon the magnets such as 45 and 61, forother cord circuits such as that containing repeater R, are placed insuch condition that any one of them may be operated upon the connectionof two lines by one of these other cord circuits.

The selection and connection of the networks for balancing lines L andL, has now been completed. A network (21) of the type such as networks21, 22 and is in connection with the transformer windings 221 and 222(at the right-hand end of repeater B, Fig. 1), because the lineselection control relay of the line L to which the righthand plug ofrepeater R is connected has an armature connected (permanently) to alead running to the bank of net bar magnets corresponding to the netbars to which networks of the type such as networks 21, 22 and 23 arepermanently connected; and a network 24 of the type such as networks 24and 25 is in connection with these transformer windings because the lineselection control relay of the line L, has an armature connectedpermanently to a lead running to the bank of net bar magnetscorresponding to the net bars to which networks of the type such asnetworks 24 and 25 are permanently connected; and a network 26 of acertain type is in connection with these transformer windings becauserelay 41 has an armature connected (permanently) to a lead running tothe bank of net bar magnets corresponding to the net bars to whichnetworks of that type are permanently connected. Of course, if line Lwere of such character that no network of the type of, say, network 24were required to balance the line, then the armature 104 of relay 41would be omitted (or, at least, the armature would not be connected tolead 84). Thus the lead from the middle armature of the line selectioncontrol relay for line L is disconnected from lead 102, therebyindicating that line L is of such character that it does not require anetwork of the type of network 24. The circuit connecting networks 21,24 and 26 to the transformer windings 221 and 222 at the right-hand endof repeater R may be traced as follows: from winding 221 through lead223, conducting member 224 of cord bar 1", spring contact 225, contactprojection 226. conducting member 227 of net bar 2, resistance 228 ofnetwork 21, conducting member 230 of net bar 2, spring contact 231,spring contact 232, through a bridging plate to spring contact 233,spring contact 234,

through a bridging plate to spring contact 235, conducting member 236 ofcord bar 1*, thence to conducting member 241 of cord bar 1 through twoparallel branches, one branch extending from conducting member 236through spring contact 237, conducting member 238 of net bar 2, network24, conducting member 239, spring contact 240 to conducting member 241,and the other branch extending from conducting member 236 through springcontact'242, conducting member 243 of not bar 2 network 26, conductingmember 244, spring contact 245, to conducting member 241, then from thisjuncture of the two branches at conducting member 241 through lead 247to winding 222. A condenser forming part of the network 21 is bridgedbetween the midpoint of resistance 228 and the midpoint of resistance246.

The circuit connecting networks, 22, 25 and 27 to the transformerwindings 248 and 249 at the left-hand end of repeater R will not betraced, since it is similar to the circuit just traced.

In order to provide for taking'care of an overflow or unusual demand forcertain types of balancing networks, lamps such as 250, 251 and 252 areprovided to indicate to the operator the type of network required whenall of the networks of any type which are capable of selection andconnection by the cross-bar switch are in use, and lamps such as 253,254, 255 and 256 are provided to indicate to the operator the cord onwhich the network is required, and variable impedance cord circuits 257,258 and 259 are provided which the operator can plug into the cord whichone of the lamps such as 253 to 256 has indicated as requiring abalancing network. The operator adjusts the impedance of the circuitsuch as 257, 258 and 259 to form a network of the type which one of thelamps such as 250 to 252 has indicated is required.

The operation of the system as regards this feature will now bedescribed on the supposition that all of the networks of the type suchas 21, 22 and 23, except network 23, are in use when the operatorinserts plugs P and P into the jacks of lines L, and L,, 4

respectively, as mentioned above. Then the cross-bar switch and itsassociatedcircuits will select and connect to transformer windings 221and 222 the network 23, instead of network 21; for the circuit betweenlead 84 and winding of pick-up magnet will be open at armature 86 ofmagnet 80, and the circuit from lead 160 through armatures 161 and 163to winding of pick-up magnet 151 will be open at armature 163, and thefollowing circuit will be energized for operating net bar pick-up magnet260 corresponding to network'23: from ground through battery 43, throughelements 44, 46, 64, 66,67, 74 '75, 76, 81, 79, 82, 73, 83, 84, 155, alead and an armature corresponding to lead 261 and arn'i'ature 262' (butassociated with the repeater cord which is in connection with network22), a lead corresponding to 263 (but associated with the last mentionedrepeater cord), extreme left-hand conducting member of the cord barthrough which not work 22 is in connection with the last mentionedrepeater cord, througha spring contact on the last mentioned cord bar tothe extreme upper conducting member of net bar 2*, lead 264, middlearmature of pick-up magnet 151, right-hand armature of winding ofpick-up magnet 260, pick-up magnet 260, left-hand armature of. magnet260, armatures 167 and 90, leads 91, 92 -and 93, armature 94 of lineselection control relay 41 to ground. I

The locking circuit'for the ick-up and locking magnets of net bar 2 wi 1be similar to the locking circuits hereinbefore traced for the net barmagnets of. net bars 2, 2, 2, 2, 2 and 2, and maybe traced from groundthrough battery 43, elements 43, 44,

46, 64, 66, 67, 74, through branch-115 and branch 75, and 135 to lead116, thence to cord bar conducting member 117, the spring contactimmediately above spring contact 243, the correspondingconducting'member of netbar 2", the Winding of locking magnet and thewinding of pick-upmagnet 260 of net bar 2", the extreme lefthand contactspring of magnet 260, lead 265 to ground- Net bars 2 and 2 will beoperated by means of pick-up circuits through windings of magnets and165and locking circuits through windings of magnets 95 and 123 inseries, and windings of magnets and'129 in series, all just ashereinbefore described. Also in the ifashion described-above, followingthe operation of magnet 260 magnet 79 releases, magnet 69 operates,magnet 41 releases, magnet 49 operates,magnet 156 re leases, magnets35and 15operate, and net bars 2" and 2 are operated by means of pick-upcircuits through magnets 171 and 184, and lockingcircuits throughwindings of magnets 171 and 206 in series and windings of magnets 184and212 in series.

However, magnet 150 does not release when armatures 177and 190 ofpick-up magnets 171 and 184 are attracted, for mag not 1.50remainsenergized over the following circuit 1 from groundthrouglixl'iattery 43, elements 44, 46, 64, 66, 67, 74, 75, 76-, 142,144, 145, 146, 152, winding of magnet 150, elementsi153, 149, 154, 84,155, 141, 156, 157, the extreme upper one of spring contacts 3 whichcooperates with net bar 2", the extreme upper conducting member of netban-2", lead 266, middle armature of magnet 260, lead 267 lamp- 253,armature 148 to ground.

The current through the circuit just trace-d lights lamp 253 and lamp-256 has already beenlighted by current from ground through the batteryat lamp 250,- lamp 250, left-hand armatureof magnet 260, left-handarn'iature of magnet 151, left-hand armature of magnet 80, leads 91, 168and 169, arm-aiure 170 of line selection control relay 35 to ground.

Lamp 256 indicates to the attendant that all of the regular networks ofthe type such as networks 21, 22 and 28 are in use and that an auxiliarynetwork of such type is demanded, and lamp 253 indicates that therepeater cord on which the auxiliary network is required is the cordcorresponding to cord bar magnet 15.

Therefore, the attendant adjusts the impedances of network 257 to form anetwork of the required type and inserts plugs 267 and 268 in jacks 269and 270, thereby inserting network 257 inseries with the parallelcircuit branches comprising networks 25 and '27, and also lighting lamp271 over a circuit will be traced hereinafter, and also breaking atspring contact 272 the circuit of magnet 15.

The circuit connecting networks 257, 25 and 27 to the transformerwindings 248, 249 may be traced as follows-: from winding 248 throughlead 273, ring conductor of jack 269 and plug 267, right-hand side ofnetwork 257,'ring conductors of plug 268 and jack 270, lead 274. theplate bridging the two lower ones of spring contacts 3 opposite net bar2, the short circuiting plate bridging the two loweronesof springcontacts 3, opposite net bar 2*, the plate bridging the two lower onesof spring contacts 3 opposite net bar 2", to cord bar cond'ucting member27 5. thence to cord bar conducting member 276 through two par-V allelbranches, one branch extendingfrom cord bar conductingmember 275 throughextreme lower spring contact 3 opposite net bar 2, :(treme lowerconducting member of net bar 2", network contact projection immediatelybelow contact projection 208, spring contact 3 immediately below contact267, to cord bar conducting member 276,. and the other branch extendingfrom cord bar conducting member 275 through extreme lower springcoiitac't 3 opposite net bar 2, extreme lower conducting member of netbar 2, network contact pro jection immediately below contact projection.214, spring contact immediately below spring contact 213, to cord barconducting member 276, then from this junction of the two branches atmember 276 through the plate bridging the middle pair of spring contacts3' opposite net bar 2 the plate bridging the middle pair of springcontacts 3 opposite the net bar 2', the plate bridgthe middle pair ofspring contacts 3 opposite the net bar 2, lead 277, the tip conductor orjack 27.0 and; plug 268, the lefthand side of network 257, the tipconductors of plug 267 and jack 269, lead 278 to transformer winding24-9.

The circuit over which lamp 271 is lighted, as mentioned above, may betraced as follows: from ground, through battery 13, elements ll, 16, 64.65, 67, 7a, 75, 76, 1- 12. 1%, through resistance 218 in parallel withthe armature of magnet 150, thence through lead 200, the sleeveconductors of jack 270 and plug 271, and lamp 271 to ground. Lamp 271remains lighted as long as the network 257 is required by the re peatercord corresponding to plug P, but when the connection through repeater Ris taken down, the lamp 271 is extinguished so that the attendant willbe advised that plugs 267 and 268 may be removed from jacks 269 and 270.

When the circuit of cord bar magnet 15 is broken at ack contact 272, asmentioned above, that magnet releases, breaking the circuit traced aboveincluding armatures 148 and 149. winding of magnet 150 and lamp 253.Therefore lamp 258 becomes 1';- tinguished. Also, magnet 150 releases,connecting-magnet 139 in parallel with resistance 218. hlagnet 139 thenoperates, causing magnet 35 to open and extinguish lamp 250 and alsocausing magnet 56 to operate.

The operation of armature 145 of magnet 56 opens a gap in the circuittraced above for cord bar magnet 15, but that circuit has already beenbroken at ack contact 272 as described above. The operation of armature220 of magnet- 56 breaks the circuit of magnet 42 at contact 55, thuscausing the breaking at 64 of the connection traced above from battery43, to lead 67. How ever, before this break at 64t occurs, armature 220by engaging spring contact 55 connects battery 136 to lead 67, thisconnection being traceable from battery 136 through elements 137, 48,50, 51, 52, 53, 54;, 55, armature 220 to lead 67. Thus magnets 69 and49, the pick-up and locking magnets of net bars 2*, 2 and 2, magnets 139and 56, and the pick-up and locking magnets of net bars 2 and 2 aremaintained energized from battery 136 until the circuit traced abovefrom lead 136 to lead 67 is broken at armature 51 or 53 by thedeenergization of magnet 36 or 30, due to the removal of plug P or P.

The breaking of the circuit of magnet 42. as mentioned above, and theconsequent release of its armatures 64: and 65 also conditions themagnets such as 45 and 61 for operation upon the connection of two linesby a repeater cord other than that of the repeater R.

Of course, it it had been required that an auxiliary net work of thetype such as networks 21, 22 and 23 be connected to transformer windings221 and 222 instead of to transformer windings 248 and 2 19, then theattendant would have plugged the network 257, or some other network ofthe same type into jacks 279 and 280 instead of into jacks 269 and 270.

Network 257 is of the same general type as networks 21, 22 and 23; butit it were required that an auxiliary networkot the same generaltype asnetworks 2 1, 25, 26 and 27 be connected to the transformer windings24:8 and 2-19, the attendant could adjust the impedance of either of thenetworks 258 or 259, (or of any one of any provided number of suchnetworks) to form the proper network and plug it into either of thejacks 281 or 282, or into any one of any number of such jacks whichmight be provided. Or the attendant could adjust the impedance of thecondenser and the lower half of the re sistances of network 257 to forma network of the required impedance and insert plug 268 into either ofthe jacks 281 or 282, leaving plug 267 disengaged from all jacks.

Any desired number of cord bars and repeater cord circuits, and anydesired number of net bars with networks of any desired impedancespermanently connected thereto, and any desired number of auxiliarynetworks of any desired impedance may be used, the number and characterof such elements desired being dependent upon the number and characterof the lines to be interconnected by repeater cords and the volume oftraflic over each line.

that is claimed is:

1. A cross-bar switch comprising a bar carrying contact means andbridging means carried by said bar for electrically connecting certainof said contact means together in one position of said contact means andbreaking said connections in another position of said contact means.

2. A cross-bar switch comprising a bar carrying yielding contactmembers, brie ging members carried by said bar for electricallyconnecting certain of said contact members together, and a bar carryingcontacts for engaging with said yielding contact members and disengagingsaid yielding contact members from said bridging members 3. A cross-barswitch comprising two movable switching bars intersecting each other,carrying cont-acts adapted to be engaged when said bars are operated,and electrical contact means adapted to conneetively engage the contactsof one of said bars when said bars and their contacts are in theirnormal or unoperated position.

4:. A cross-bar switch comprising two bars intersecting each other,contact means on one of said bars, contact means on said other baradapted to engage said first contact means upon operation of said bars,and contact means engaging said first contact means, said last-mentionedcontact means being dis engaged from said first contact means uponoperation of said bars to engage said first and second contact means.

A selective switch comprising coordinately arranged sets of back, front,and active contacts and means to separately operate said sets ofcontacts.

6. A selective switch comprising coordinately arranged sets of back,front, and active contacts and electromagnetic means to separatelyoperate said sets of contacts.

7. A selective switch having active contacts, back contacts forestablishing connec- In witness whereof I hereunto subscribe 20 my namethis 11th day of October, A. D., 1923.

ROY D. CONWAY.

